It is common in automotive applications to illuminate switch assemblies so that they can be easily located and identified in a darkened environment, such as nighttime driving. These switches are usually located on a vehicle dashboard or on an interior door trim panel.
It is also common to employ elastomeric keypad switch assemblies having depressible key caps for moving an electrically conductive pellet mounted on its underside into and out of engagement with contacts on a printed circuit board. A common method of illuminating such a switch assembly is to mold the keypad out of a clear or translucent material and then paint the visible surface. A laser is then employed to etch a symbol or word on the key which exposes the clear material. Light can then be transmitted through the exposed etched symbol or word in the key caps of the keyboard by an optical conductor located beneath the keypad. Another obvious way to illuminate the switch assembly is to provide for an overhead lighting system and shine a light onto the surface of the switch assembly.
In copending application, Ser. No. 08/279,147, filed Jul. 22, 1994, and assigned to the same assignee as the present invention, there is disclosed an elastomeric keypad switch assembly in which a halo light effect surrounding the key caps is provided.
That keypad switch assembly comprised a planar optical conductor for connection to a light source, a separate printed circuit means having a transparent base secured to the optical conductor, and a one piece keypad made from an elastomeric material which overlaid the printed circuit means. The keypad had an opaque base a plurality of opaque key caps each having a bottom surface carrying an electrically conductive pellet and located above a pair of contact ends on printed circuit lines of the printed circuit board, thin annular translucent webs for integrally connecting the key caps to the keypad and with the key caps each having an outer peripheral side wall which was spaced inwardly from a side wall of the keypad surrounding the key caps and with the thin annular webs being integral with the side wall of the keypad adjacent its underside and integral with the key caps adjacent its bottom side. The thin annular webs functioned to bias the caps toward a normal position and which the pellets were spaced from the contact ends of the printed circuit lines. The key caps were depressible to deflect the annular webs to move the pellets to engage the contact ends of the printed circuit lines to complete a circuit. The annular webs functioned as both a spring to bias the key caps toward their normal position and to transmit light therethrough and with the side walls of the keypad serving to direct light through the webs to create a visible halo lighting effect surrounding the key caps.